1. Field of the Invention
The field of art to which this invention pertains is hydrocarbon processing. It particularly relates to an improved process for the production of an isoparaffin-olefin alkylation product through hydrogen fluoride catalysis.
2. Prior Art
The production of higher molecular weight isoparaffins, haing valuable antiknock properties as motor fuel, is of considerable importance in the petroleum refining industry. Furthermore, the growth of the synthetic fibers and plastics industries has increased consumption of aromatic hydocarbons such that less are available for use as high octane motor fuel blending components. Thus, a demand for higher molecular weight isoparaffins as blending agents for fuels has materialized. Accompanying this demand for higher octane blending components is a demand for greater quantities of the blending components themselves due to the incessant increase in world gasoline consumption.
A convenient source of such higher molecular weight isoparaffins is the catalytic alkylation of lower boiling isoparaffinic hydrocarbons, such as isobutane, with olefinic hydrocarbons, such as propene and butenes. It is well known in the art that catalytic alkylation using acid catalysts, such as hydrofluoric acid, has become an important tool for preparing alkylated hydrocarbons. However, there is an inherent feature of conventional designs of hydrogen fluoride-catalyzed alkylation process units which contributes to poor use of internal streams. Unreacted isoparaffins leaving the reaction zone of an alkylation process are recycled and mixed with fresh feed to provide, within the reaction zone, an excess of isoparaffinic components. Isoparaffins which are thusly recycled are referred to as recycle isoparaffins. In order to beneficially affect the product quality, the recycle isoparaffins must be thoroughly mixed with other feed components such as fresh isoparaffins and fresh olefins before contact with the catalyst phase occurs. Due to the design of conventional alkylation process units the isoparaffins exiting the catalyst regeneration zone contain hydrogen fluoride as a separate phase, and this hydrogen fluoride phase can catalyze undesirable reactions which would occur upon mixing of fresh olefins with the isoparaffins. These undesirable reactions would produce contaminants which would remain in the final alkylate product and lower its quality. For this reason these regeneration zone isoparaffins are not recycled to mix with fresh feed, and their utility as recycle isoparaffins is lost. Our invention solves this prior art problem by eliminating the hydrogen fluoride phase from the regeneration zone isoparaffins and utilizing them as recycle isoparaffins.